Driving digits on a found fragment of Amstrad electronics

Birketts in Lincoln is an Aladdin's cave of weird and wonderful old electronics. The last time I was there I picked up this lovely fragment of board with two seven-segment displays. 

If nothing else I just wanted to see what colour the LEDs were and maybe harvest the 2-digit display.

I guess it's from some kind of stereo equipment, although a quick image search doesn't turn up anything with a 2-digit display like this. 

As you can see, someone has reverse-engineered it, added and labelled some wires and has also bodged a transistor into the data line. They've written 'Data is true logic' on the board. I don't know whether that means that the driver chips' serial inputs require true logic and the transistor ensures this, or that you should make sure that your data signal is logic level. Either way, this arragment works when I hook it up to my RC2014 which works at TTL levels. I'm curious about whether that transistor allows a 3.3V input.

I don't think I've played with a 74164 (serial to parallel shift register) before, so this has been a lot of fun. It has a clocked serial input, meaning that you can simply wire up buttons to make it work:

This was reasonably successful, although some debounce would have helped. At least it helped me to understand how the serial input was working. 

It didn't take too long to write a program in assembly to drive this. I bit-banged lines from my digital i/o module. In the video you can see the LEDs on that module flashing as it serialises the data into reset, clock and data signals. 

I'm not sure why a reset signal is required. I've put in some delays for the 'shake' effect in the electronic dice program but I presume that with a faster data speed, you wouldn't even see that. In my case the reset line isn't connected to both digits anyway, 

It's very elegant, just two jellybean logic chips make this work.  Having said that, I don't think LS logic chips should be driving LED segments directly but it doesn't surprise me that Amstrad did this. 

One challenge was that the segments aren't wired in any sensible order, and each is different (meaning you need a different 'font' for the left and right-hand digits!) To be fair, this is a single-sided board, so I guess the layout guy just laid tracks in the most convenient way. 

I don't know what else to do with this. The segments are that lovely yellow-green, it'll be nice to use them in something else.